Figure 6.

A Speculative Model for Dynamic Interactions of AtTEN1.

(A) AtTEN1 may play a role in regulating the switch of telomeres from the telomerase unextendable to the extendable state. The CST complex is proposed to form a protective cap for Arabidopsis telomeres. Unlike STN1 and CTC1, TEN1 is not associated with enzymatically active telomerase. Thus, the exchange of TEN1 for POT1a may help to convert telomere ends into a telomerase extendable state. Once dislodged from STN1, TEN1 is free to form “activated” higher order structures (illustrated for simplicity as a hexamer) with chaperone activity. Association of HMW TEN1 with CTC1 could facilitate conformational changes in CTC1 that promote the access of telomerase or DNA Pol-α to the chromosome end.

(B) In response to thermal stress, TEN1 is dislodged from STN1 and assembles into “activated” HMW complexes that stabilize CTC1 and protect telomeres from deletional recombination (TRD). C, CTC1; S, STN1; T, TEN1; Pa, POT1a.